For centuries, the purpose of the narwhal’s tusk, or the “unicorn of the sea,” has perplexed scientists. This evolutionary mystery defies many known rules regarding the teeth of mammals.
A recent study suggests that this whale species uses its tusk to gauge the salinity of water and search for food. Additionally, males may rub their tusks against each other as a previously unknown sensory behavior.
Narwhals can reach lengths of 4 to 4.5 meters and weigh between 1 to 1.6 tons. Many individuals possess a long tooth (or tusk) measuring up to 2.4 meters, protruding from the left side of the upper jaw. The unique spiral groove on this tusk, its asymmetry towards the left, and its peculiar presence on most males and some females are distinctive features among mammalian teeth.
After four expeditions to the Arctic region near Canada to study narwhals, Martin Nweeia from Harvard School of Dental Medicine discovered that the narwhal’s tusk, despite its hard exterior, has remarkable sensitivity. With 10 million tiny nerve connections running from the tusk’s nerve center to its outer surface, the tusk acts like a highly sensitive membrane capable of detecting minute changes in temperature and pressure in the seawater.
Because narwhals can detect subtle changes in their environment, they are able to determine the salinity of the water as well as disturbances around their prey, which aids their survival in the icy Arctic habitat.
In the past, scientists have proposed various hypotheses to explain the purpose and function of this tusk, but no single explanation has been universally accepted. One common hypothesis suggests that the long, unusual tooth is used to display aggression among males during competition for dominance. Another theory posits that it serves as a secondary sexual characteristic, similar to the plumage of a male peacock or the mane of a male lion.
This recent discovery opens new avenues for scientific investigation.
